Snaps work well flat on the floor, but as a change up, I'll set them on their side against baseboards etc. Use double sided tape, a small nail or screw to hold them.

I had good luck testing Moletox ( zinc phosphide). I found a container unopened at a thrift shop. Set out a pile the size of a quarter in my garage where trap shy mice were evading my snap traps.
They fed a couple times are gone. About half the bait remains for next trespassers.